Catheter exchange system with detachable luer fitting

ABSTRACT

A small diameter balloon dilatation catheter having a shaft formed from hypodermic tubing is provided with a detachable luer fitting on its proximal end. The luer fitting may be removed and an extension wire attached to the proximal end of the catheter. A larger diameter catheter then may be advanced over the smaller catheter utilizing the smaller catheter to guide the larger catheter to the stenosis being treated. In another aspect of the invention, a guiding sheath assembly is provided which permits catheter exchanges involving such small diameter catheters having integral guidewires. In one protocol such a catheter may be exchanged for a conventional balloon dilatation catheter with a movable guidewire by removing the dilatation catheter, advancing the sheath over the guidewire, then removing the guidewire and inserting the replacement catheter. Similarly, a catheter having an integral guidewire may be exchanged for a similar catheter by first removing the luer fitting at the proximal end of the catheter, then attaching a wire extension to the proximal end of the catheter, then advancing a sheath over the extension and catheter to locate the distal end of the sheath in proximity to the stenosis, then removing the catheter through the sheath and replacing that catheter with a new catheter inserted through the sheath.

This application is a continuation of application Ser. No. 07/303,549,filed Jan. 27, 1989, now U.S. Pat. No. 5,035,686.

FIELD OF THE INVENTION

This invention relates to balloon dilatation catheter systems used inpercutaneous transluminal coronary angioplasty.

BACKGROUND OF THE INVENTION

This invention relates to improvements in small diameter low profiledilatation catheters used in angioplasty and particularly coronaryangioplasty. More particularly, the invention concerns the type ofdilatation catheter which incorporates a wire-like shaft that issufficiently torsionally rigid so as to be steerable thereby enablingthe catheter to be selectively guided and steered to the desiredlocation in the patient's coronary arteries.

In performing coronary angioplasty, it often occurs that the physicianmay wish to use a catheter different than the on originally insertedinto the patient. For example, this may occur if the initial selectionof catheter balloon size was inappropriate to treat the patient'sstenosis or some other event occurs that would make use of a differentcatheter desirable. When the catheter is of the type that uses aseparate movable guidewire, the catheter may be exchanged in a wellknown procedure in which an exchange wire is substituted for the movableguidewire (or the length of the guidewire is extended with an extensionwire); then the catheter is withdrawn over the exchange wire and thereplacement catheter is threaded over the exchange wire and is therebyguided to the stenosis. By maintaining the guidewire in position duringthe exchange procedure, the replacement catheter is easily and quicklyadvanced to the stenosis.

The foregoing catheter exchange procedure has not been usable with smalldiameter low profile dilatation catheters of the type that incorporatean integral guidewire because the balloon catheter cannot be separatedfrom the guidewire. Thus, when it is desired to exchange one suchdilatation catheter for another, the typical procedure is to withdrawthe entire catheter and integral guidewire and then replace it with thedesired catheter. Withdrawal of the catheter, however, results in lossof position of the catheter in the stenosis. As a result, the nextplaced catheter must be re-manipulated through the patient's arterialsystem to position the balloon in the stenosis. The replacement of thecatheter typically involves time consuming manipulation and steering toguide the catheter to place its balloon within the stenosis. Theadditional procedure increases somewhat the risk of trauma to thepatient.

A similar problem is presented when it is desired to exchange aconventional movable guidewire dilatation catheter for a catheter of thetype having an integral guidewire. Again, in order to make such anexchange, it has been necessary to remove completely the movableguidewire and the dilatation catheter to permit insertion of theintegral guidewire type of catheter. Because there is nothing to guidethe catheter directly to the stenosis, it is necessary for the physicianto go through all the manipulations necessary to steer and guide the newcatheter to the stenosis.

It would be desirable, therefore, to provide a system by which catheterexchanges involving small diameter low profile dilatation cathetershaving an integral guidewire could be effected easily, quickly, withoutloss of position and with minimal trauma. It is among the objects of theinvention to provide such a system.

SUMMARY OF THE INVENTION

In accordance with one aspect of the invention, a small diametercoronary dilatation catheter has a shaft formed from stainless steelhypodermic tubing. The distal end of the shaft is of increasingflexibility and terminates in a highly flexible distal tip. Thedilatation balloon is mounted to the shaft near the distal end. Theinterior of the balloon is in communication with the lumen extendingthrough the hollow shaft. The balloon may be inflated and deflated witha liquid by a syringe or other suitable inflation device attached to theproximal end of the shaft by a luer fitting carried at the proximal endof the shaft. In the present invention, the luer fitting is detachablefrom the hypodermic tubing so as to present a smooth continuous diameterat the proximal end of the catheter shaft. The luer fitting includes acollet and nut arrangement by which the luer fitting can grip securelythe tubular proximal end of the dilatation shaft. After the luer fittingis detached, an extension wire is connected to the proximal end of thecatheter shaft to extend its length. With its length so extended, a newcatheter is advanced over the extension and along the shaft, followingthe shaft which thus serves as a guidewire to guide the catheter to thearterial branch to be treated. The small diameter dilatation cathetermay remain in the patient and may serve as a guidewire for the largercatheter should it be desired to direct the larger catheter to otherregions in the coronary anatomy. Should it be desired to again use thesmall diameter dilatation catheter with integral guidewire, the outercatheter and extension wire can be removed and the luer fitting can bereplaced on the proximal end of the small diameter dilatation catheterto enable it to be used again to dilate a narrow stenosis.

Should it be desired to replace the small diameter dilatation catheterwith another catheter also having an integral guidewire, the luerfitting is detached from the proximal end of the shaft and an extensionwire is attached to the proximal end of the catheter shaft. In anotheraspect of the invention, an elongate flexible sheath then is advancedover the extended length dilatation catheter and into the patient'scoronary artery close to the site of the stenosis. The dilatationcatheter then is withdrawn through the sheath which remains in place.The new catheter then can be advanced through the sheath directly to thelocation in the coronary artery to be treated. In this instance, thesheath serves to maintain direct and quick access to the branch arterybeing treated.

In still another protocol that may be practised in accordance with theinvention, a conventional dilatation catheter having a removableguidewire may be exchanged for the small diameter fixed guidewire typeof dilatation catheter described above. In this aspect of the invention,an extension is fitted to the guidewire. Then the conventionaldilatation catheter is removed from the patient, leaving the guidewirein place within the stenosis. The elongate flexible sheath, discussedabove, then is advanced over the guidewire to the location of thestenosis. The guidewire and extension then may be removed and thecatheter with integral guidewire may be inserted into the sheath and beguided directly to the stenosis.

It is among the general objects of the invention to provide an improvedsystem for performing catheter exchanges involving a small diameterdilatation catheter having an integral guidewire.

Another object of the invention is to provide a small diameterdilatation catheter having a guidewire like tubular shaft in which aluer fitting at the proximal end of the shaft is detachable.

DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and advantages of the invention will beappreciated more fully from the following further description thereofwith reference to the accompanying drawings wherein:

FIG. 1 is a fragmented illustration of a small diameter dilatationcatheter having an integral guidewire-like shaft;

FIG. 2 is an enlarged cross sectional illustration of the proximal endof the dilatation catheter shaft and the luer fitting;

FIG. 3 is an exploded illustration of the luer fitting;

FIG. 4A is an illustration of the ends of the extension wire and theproximal end of the dilatation catheter after the luer fitting isremoved from the dilatation catheter and before the catheter and wireare joined;

FIG. 4B is a cross-sectional illustration of the connection between theguidewire extension and proximal end of the catheter;

FIG. 5 is a diagrammatic illustration of a larger catheter being passedover the shaft of the smaller diameter dilatation catheter, with theshaft serving as a guidewire to guide the larger catheter to thestenosis;

FIG. 6 is a diagrammatic illustration of the system of a flexibleguiding sheath and inner sheath which may be used to facilitateexchanges of dilatation catheters having an integral guidewire;

FIG. 7A is a fragmented illustration of a coronary arterial system witha guide catheter in place and a dilatation catheter having a detachableluer fitting extending through the guide catheter and into the stenosisof a coronary artery;

FIG. 7B is an illustration similar to FIG. 7A with the proximal luerfitting of the catheter detached, a guidewire extension attached to theproximal end of the dilatation catheter and the dual guiding sheatharrangement advanced over the balloon dilatation catheter and into thecoronary artery in proximity to the stenosis; and

FIG. 7C is an illustration of the arterial and catheter system of FIG.7B with the dilatation catheter and inner sheath removed, leaving theouter sheath in place and in readiness to receive another dilatationcatheter having an integral guidewire.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

FIG. 1 illustrates, generally, a small diameter balloon dilatationcatheter 10. The catheter may be of the order of 175 cm long. Itincludes an elongate shaft 12 formed from hypodermic tubing. A polymericdilatation balloon 14 is mounted to the distal end of the catheter. Thedistal tip 16 of the catheter is of increasing flexibility in a distaldirection and, typically, may be formed from a helical coil ofradiopaque material. The shaft 12 is sufficiently torsionally rigid sothat it may transmit rotation from the proximal to the distal end of thecatheter when the distal end is in the coronary arteries. In order thatthe device may be selectively steered through the branches of thecoronary anatomy, the distal tip 16 is formed so that it may be bent toa slight "J" shape illustrated in phantom at 17. A luer fitting 18 isattached to the proximal end of the shaft 12 to enable attachment of aninflation device such as a syringe (not shown) to inflate and deflatethe balloon 14 with a suitable fluid, such as radiopaque contrastliquid. Such a catheter is disclosed in more detail in U.S. patentapplication Ser. No. 729,541, filed May 2, 1985.

As shown in FIGS. 2 and 3, the luer fitting, indicated generally at 18,includes a hub 20 having a socket 22 at its proximal end and a distallytapering bore 24 located distally of the socket 22. An aperture 26 isformed at the distal end of the hub 20 and receives the proximal end ofthe catheter shaft 12. A collet 28 having distally extending fingers 30is provided with a central bore 32, also to receive the proximal end ofthe shaft 12 of the catheter. A compressible gasket 34 formed from anelastomeric material such as silicone rubber, and also provided with acentral bore 36, abuts the proximal face of the collet 28. The bore 36of the gasket 34 receives the proximal end of the catheter shaft 12. Ashaft stop member 38 is provided with a central aperture 40 which tapersin a proximal direction. The bore 40 tapers to a diameter that issmaller than the diameter of the proximal end of the catheter shaft 12and, therefore, serves as an abutment for the proximal end of the shaft12 as shown in FIG. 2, to prevent it from extending proximally beyondthe stop member 38. The collet 28, gasket 34 and stop member 38 aresecurely retained between the hub 20 and a luer body 42 having athreaded distal end 44 that screws into the socket 22 of the hub 20. Thedistal end of the luer body 42 has a socket 46 which receives stopmember 38, the gasket 34 and the proximal portion of the collet 28. Thedistal fingers 30 of the collet bear against the tapered bore 24 in thenut. When the luer body 42 is screwed into the nut 20, the colletfingers 30 constrict about the proximal end of the shaft 12 to securelylock the luer fitting 18 in place. The gasket 34 also is compressed toeffect a secure liquid seal about the shaft 12. The proximal end of theluer body 42 has a luer socket 48 adapted to be connected to a syringeor other inflation/deflation device. Thus, it will be appreciated thatthe entire luer fitting 18 may be detached from the proximal end of theshaft 12 simply by unscrewing the hub 20 and luer body 42 to release thecollet and permit the assembly to slide off of the proximal end of theshaft 12.

In accordance with the invention, the proximal end of the shaft 12 isformed to define a socket 50 adapted to receive the distal end of anextension wire 52 as illustrated in FIGS. 4A and 4B. The distal end ofthe extension wire is constructed in a manner that enables it to bedetachably connected to the socket 50 in a manner described in detail inpending application Ser. No. 206,008 filed Jun. 13, 1988 entitledRemovable Guidewire Extension, reference being made to said applicationfor the full details of the extension wire connection. FIGS. 4A and 4Billustrate, somewhat diagrammatically, the nature of the connection. Inbrief, the distal end of the extension wire carries a helical coil 54that detachably connects within the socket 50.

One manner in which the system may be used is illustrated in FIG. 5. Inaccordance with accepted percutaneous transluminal coronary angioplastytechniques, a guide catheter 51 is percutaneously inserted into afemoral artery 53 in the region of the groin and is advanced along theaorta 55 to place the distal tip of the guide catheter 51 at theentrance to the coronary artery 57. Once the guide catheter is in place,a balloon dilatation catheter 10 is advanced through the guide catheter51 and is manipulated to position its balloon 14 within the the stenosis59 to be treated. Should the physician wish to change to a largercatheter having a larger balloon, the inflation device is detached fromthe luer fitting and the luer fitting 18 is detached from the cathetershaft 12 by unscrewing the luer body 42 to loosen the fitting 18. Theextension wire 52 then is attached to the socket 50 at the proximal endof the catheter shaft 12. The larger catheter 56 then may be advancedover the extension wire 52 and the catheter shaft 12 which guides thelarger catheter 56 through the coronary arteries 57 directly to thestenosis 59. Depending on the dimensions of the catheters and the extentto which the balloon 14 on the small diameter dilatation catheter 10 canbe collapsed, the larger catheter 56 may be passed over the balloonportion 14 of the smaller catheter 10. Alternately, the balloon 58 ofthe larger catheter 56 can be placed in the stenosis by advancing boththe smaller and larger catheters 10, 56 distally until the balloon 58 ofthe larger catheter 56 is in the stenosis (if the coronary anatomypermits). The balloon 58 of the larger catheter 56 then may be inflatedto perform the further dilatation with the larger size balloon.

In another mode of operation, it may be desired to replace the smalldiameter dilatation catheter 10 with another, small diameter dilatationcatheter having an integral guidewire. FIG. 7A illustrates a guidecatheter in place in the patient's coronary arterial system and a smalldiameter dilatation catheter 10 extending through the guide catheter 51,into a coronary artery 57 and into the stenosis 59. Such a catheterexchange requires removal of the initial catheter 10. However, in orderto maintain an ability to quickly and easily reach the stenosis with thenext catheter, the luer fitting 18 is detached and an extension wire 52is fitted to the socket 50 at the proximal end of the shaft 12 (FIG.7B). As shown in FIG. 7B, a tubular guide sheath assembly 60 then isadvanced over the extension wire 52 and catheter shaft 12. The sheathassembly 60 is advanced to place its distal end within the coronaryartery 57 as close to the stenosis 59 as possible. Once the sheath 60has been so placed, the catheter 10 may be withdrawn, possibly togetherwith a portion of the sheath assembly as described below. As shown inFIG. 7C, the remaining portion of the guide sheath assembly 60 thenprovides a clear and direct path along which the replacement cathetermay be advanced and guided directly to the stenosis 59.

The foregoing sheath assembly 60 is selected and dimensioned withreference to the catheters that are to be passed through it so that thecatheters may pass freely. As discussed below, the guide sheath assembly60 may be formed in two elements including an inner sheath and an outersheath. The outer sheath may be used alone with relatively largerdiameter catheters and the outer sheath and inner sheath may be usedtogether with very small diameter catheters or guidewires. The innerdiameter defined by the sheath arrangement, whether the outer sheathalone or the combination of outer and inner sheath should be such as topermit free passage of the catheter or guidewire with which it is to beused but without having so much clearance that the ability of the sheathto be pushed over such a catheter or guidewire would be impaired.

The guide sheath assembly 60 is illustrated in FIG. 6 and includes anouter sheath 62 and an inner sheath 64 that is received in the outersheath 62. Each of the outer and inner sheaths 62, 64 is provided with aproximal fitting 66, 68. The fittings ar detachably connectable to eachother with luer tapers. The inner sheath 64 serves to fill sufficientlythe annular space between the small diameter catheter shaft or guidewireand the inner lumen of the outer sheath 62 to provide axial strength or"pushability" for the sheath assembly as it is advanced over thecatheter or guidewire. Of course, if the catheter is of sufficientdiameter, the inner sheath 64 may be omitted and the procedure may beeffected with the outer sheath alone. When both inner and outer sheathsare used, after the sheath assembly has been advanced into position, theinner sheath 64 is removed to present the full diameter lumen of theouter sheath and to enable insertion of the replacement dilatationcatheter 10 with integral guidewire.

As mentioned above in another protocol, the small diameter catheter withintegral guidewire may be exchanged for a conventional balloondilatation catheter having a removable guidewire. The small diametercatheter with integral guidewire may be removed as described above inconnection with FIGS. 7A-7C. From the configuration shown in FIG. 7C inwhich the outer sheath 62 provides a direct path to the stenosis 59, aconventional guidewire is advanced through the sheath 62 so that itsdistal tip can extend through the stenosis 59. A guidewire extensionthen is attached to the proximal end of the guidewire. The sheath 62then may be withdrawn, the guidewire arrangement maintaining position inthe stenosis. After the sheath 62 is withdrawn, a conventional over thewire catheter can be passed over the guidewire to direct its distal enddirectly to the stenosis.

In still another protocol, a conventional dilatation catheter having aremovable guidewire may be exchanged for a small diameter catheterhaving an integral guidewire. In order to exchange that catheter for acatheter having an integral guidewire, a guidewire extension 52 may beattached to the proximal end of the guidewire. The conventional balloondilatation catheter then may be removed over the extended guidewire. Asheath assembly 60 including both the outer sheath 62 and inner sheath64 then is advanced over the guidewire to locate the distal end of theouter sheath 62 adjacent the stenosis 59. The inner sheath 64 andguidewire then may be removed leaving the configuration shown in FIG. 7Cof an open outer sheath 62 through which the small diameter catheterwith integral guidewire may be advanced directly to the stenosis 59.

By way of example, for use with a small diameter dilatation catheterhaving an integral guidewire shaft where the shaft is of the order of0.022" diameter and a conventional guidewire having a diameter of theorder of 0.016", the outer sheath may be about 125 cm long and beapproximately 0.058" outer diameter having a wall thickness of the orderof 0.009". The outer sheath 62 is formed to include a proximal portion67 and a distal portion 69. The proximal portion 67 preferably is formedfrom high density polyethylene and is stiffer than the distal portion 69which preferably is formed from a more flexible linear low densitypolyethylene. The more flexible distal portion is desired so that theouter sheath 62 is flexible and can follow the tortuous coronaryanatomy. The proximal section 67 is about 100 cm long and the distalportion 69 is about 25 cm long. The proximal and distal portions 67, 69are joined at a heat bond, indicated at 70.

A stainless steel helical coil 72 is mounted on the outside of thedistal end of the outer sheath 62 and is about 15 cm in length. Thespring may be formed from wire about 0.002" diameter and serves toenhance the radiopacity of the distal portion of the outer sheath sothat it may be visualized fluoroscopically. The coil 72 preferably iscoated with a lubricious material such as a polyurethane silicone blend.The coil 72 is attached only at its ends to the distal section 69 by anappropriate adhesive, preferably cyanoacrylate. The individual coilsbetween the ends of the coil 72 are spaced very slightly from each otherso that the distal portion of the outer sheath in the region of the coil72 remains highly flexible. Upon placement of an axial compressive loadon the coil 72, the individual coils butt against each other to form arelatively rigid, inflexible tubular column. This is desirable whenwithdrawing a balloon catheter through the outer sheath to insure thatthe balloon, which will interfere with the distal tip of the catheter,will not cause column buckling of the distal tip of the catheter. Shouldthere be sufficient interference between the balloon and the distal endof the catheter to cause any appreciable column compression, the coil 72rigidifies to provide support. The spacing of the coils should be justsufficient to permit the coil to retain its flexibility when it is notunder an axial compressive load. For example, a few ten thousandths ofan inch spacing between coils should be sufficient.

A soft distal tip 74 is attached to the distal tip of the distal section69, distally of the coil 72. The distal tip 74 may project distally ofthe polyethylene distal section 69 approximately 2.5 mm. It may beformed from a soft elastomeric material, preferably one which is astyrene ethylene/butylene styrene(s-eb-s) block copolymer.

The inner sheath 64 which, for example, may be passed over a 0.016" or0.018" diameter guidewire is approximately 0.034" outer diameter and mayhave an inner diameter of the order of 0.026". The distal tip of theinner sheath 64 is tapered. The inner sheath is slightly longer than theouter sheath so that when the inner sheath is advanced fully into theouter sheath, the distal tip of the inner sheath will extend about 1.5cm beyond the distal tip of the outer sheath.

The luer fittings 68, 66, respectively, of the inner and outer sheaths64, 62 are injection molded onto the proximal ends of the tubularsheaths. The proximal luer fitting 68 of the inner sheath 64 has apurging port 76 which communicates with the lumen of the luer fitting 66on the outer sheath when the two sheaths are connected. The purging port76 permits air to be purged from the inner and outer sheathssimultaneously by flushing saline solution through the proximal luerfitting 68.

From the foregoing, it will be appreciated that the invention provides ameans by which catheter and guidewire exchanges can be performed quicklyand expediently with minimal risk to the patient and without losingcatheter or guidewire position. The invention enables such an exchangeto be made for a catheter of the type having an integral, non-detachableguidewire as well as for a conventional movable guidewire catheter.Although the foregoing description of the invention has made referenceto balloon dilatation catheters, it should be understood that theadvantages of the invention also may be used with other catheters havingboth movable guidewires and integral guidewires. For example, theinvention may be practised to effect catheter changes with lasercatheters, heater probe catheters and the like.

It also should be understood, however, that the foregoing description ofthe invention is intended merely to be illustrative thereof and thatother modifications and embodiments may be apparent to those skilled inthe art without departing from its spirit.

Having thus described the invention what we desire to claim and secureby letters patent is:
 1. A balloon dilatation catheter comprising:atubular shaft having tubular distal and proximal ends and defining alumen extending therethrough; the tubular shaft being torsionally rigidto transmit manipulation of the shaft from its proximal end to movementof its distal end as well as being circumferentially rigid; a dilatationballoon mounted to the distal end of the shaft and in communication withthe lumen; a fitting for communicating with the lumen, the fitting beingdetachably and securely locked to the proximal end of the shaft, suchthat manipulation of the fitting by its proximal end moves the distalend of the shaft.
 2. A balloon dilatation catheter as defined in claim 1wherein the fitting comprises a luer fitting.
 3. A balloon dilatationcatheter as defined in claim 2 wherein said fitting comprises:a hollowhub having a passageway extending therethrough and adapted to receivethe tubular proximal end of the shaft, the interior of the hub having adistally tapering surface; a collet having a central bore therethroughadapted to receive the tubular proximal end of the shaft, the colletbeing receivable within the bore of the hub, the collet having aplurality of axially extending fingers, the distal ends of the fingersbeing tapered to mate with the tapered surface in the hub wherebydrawing together of the hub and collet will cause the fingers of thecollet to constrict tightly about the tubular shaft; a luer bodythreadably connected to the proximal end of the hub, said luer bodyhaving means for urging the collet distally into engagement with thetapered surface of the interior of the hub when the luer body and hubare screwed together.
 4. A catheter as defined in claim 3 wherein saidmeans comprises:a stop member carried by the luer body, the stop memberbeing constructed to engage the proximal end of the tubular cathetershaft to preclude movement of the shaft proximally of the stop member,the stop member having an aperture formed therethrough to permit fluidcommunication between the lumen in the shaft and the interior of theluer body; and a compressible gasket disposed between the stop memberand the collet, the gasket having a hole formed therethrough whichreceives the tubular shaft of the catheter.
 5. A catheter as defined inclaim 4 wherein the stop member has at its distal face a proximallytapering bore, the proximal end of the taper defining a smaller diameterthan the diameter at the proximal end of the tubular shaft.
 6. A balloondilatation catheter as claimed in claim 3, further comprising acompressible gasket having a central bore for receiving the tubularshaft and wherein the luer body has a hollow bore at its distal endadapted to receive the gasket, such that when the luer body and the hubare screwed together, the gasket is compressed and securely grips thetubular shaft.
 7. A balloon dilatation catheter as claimed in claim 6,further comprising a stop member with a central bore for receiving theproximal end of the tubular shaft, the stop member being adapted formounting within the hollow bore of the luer body proximally of theresilient sealing gasket, the stop member limiting proximal movement ofthe tubular member with respect to the fitting.